It is well known that the purity of DNA and RNA used in scientific and medical research is a critical factor in the success of such research. For example, gene transfer experiments in cell cultures, immunization using DNA-based vaccines and DNA sequencing projects are a few of the research areas where DNA of high purity is essential for project success. Sufficiently pure DNA is not normally attainable using traditional methods of DNA isolation. Furthermore, the process of isolating and purifying DNA is a major rate-limiting step in molecular biology. Traditional methods of isolating pure DNA have typically involved toxic chemicals such as phenol/chloroform extraction procedures, and very long centrifugation times such as in Cesium Chloride banding procedures. Not only are such procedures slow and costly, they also represent a health risk to laboratory staff and demand the usually expensive disposal of hazardous chemicals. Furthermore, despite careful preparation, DNA prepared using these methods may not always be free of RNA, proteins and chromosomal DNA.
As a result, the demand for safe, high quality and rapidly obtainable DNA preparations grown in bacteria such as E. coli has risen steadily and a variety of commercial kits have become available to meet a wide range of DNA purification needs. However, a number of these kits suffer from disadvantages, ranging from high price to failing to produce the desired quality and yield.
It is known that DNA will bind to silicon-containing materials such as glass slurries and diatomaceous earth. In fact, DNA purification kits are available which make use of these silicon-containing substances. For example, Bio 101 offers the GENECLEAN.TM. kit which makes use of a glass slurry and sodium iodide (binding buffer) and BioRad.TM. offers a plasmid purification kit using diatomaceous earth (Celite.TM.) suspended in guanidine hydrochloride buffer.
U.S. Pat. Nos. 5,503,816 and 5,525,319 and 5,693,785 by Woodard et al. describe the use of silicate compounds for DNA purification. The disadvantage with these materials is that the required silicate material is not readily commercially available in the appropriate form, and typically must be prepared requiring additional time for DNA isolation procedures.
U.S. Pat. Nos 5,438,129 and 5,625,054 describe DNA isolation procedures which utilize flourinated Celite.TM., flourinated silicon dioxide or flourinated aluminum hydroxide. These inventions require the use of toxic chemicals to create the flourinated surfaces to which the DNA will bind. In addition, chaotropes which are also toxic, are still required for these procedures.
U.S. Pat. Nos. 5,534,054 and 5,705,628 both disclose methods for isolating DNA which do not require the use of toxic chaotropic agents. The former patent discloses the use of silicon tetrahydrazide for the purification of DNA, but the preparation of the binding material requires the use of toxic chemicals which can lead to conditions such as nausea and temporary blindness. The latter of the patents relates to a non-specific, reversible binding of DNA particles using magnetic microparticles.